Fermi surface electron-hole instability of the (TMTSF)2PF6Bechgaard salt revealed by the first-principles Lindhard response function

• Published in: Journal of physics. Condensed matter Vol. 32; no. 34
• Main Authors: Guster, Bogdan, Pruneda, Miguel, Ordejón, Pablo, Canadell, Enric, Pouget, Jean-Paul
• Format: Journal Article
• Language: English
• Published: 27.05.2020
• ISSN: 1361-648X
• DOI: 10.1088/1361-648X/ab8522

We report the first-principles DFT calculation of the electron-hole Lindhard response function of the (TMTSF)2PF6Bechgaard salt using the real triclinic low-temperature structure. The Lindhard response is found to change considerably with temperature. Near the 2kFspin density wave (SDW) instability it has the shape of a broad triangular plateau as a result of the multiple nesting associated with the warped quasi-one-dimensional Fermi surface. The evolution of the 2kFbroad maximum as well as the effect of pressure and deuteration is calculated and analyzed. The thermal dependence of the electron-hole coherence length deduced from these calculations compares very well with the experimental thermal evolution of the 2kFbond order wave correlation length. The existence of a triangular plateau of maxima in the low-temperature electron-hole Lindhard response of (TMTSF)2PF6should favor a substantial mixing ofq-dependent fluctuations which can have important consequences in understanding the phase diagram of the 2kFSDW ground state, the mechanism of superconductivity and the magneto-transport of this paradigmatic quasi-one-dimensional material. The first-principles DFT Lindhard response provides a very accurate and unbiased approach to the low-temperature instabilities of (TMTSF)2PF6which can take into account in a simple way 3D effects and subtle structural variations, thus providing a very valuable tool in understanding the remarkable physics of molecular conductors.